1. Field of the Invention
The present invention is related to a seamless capsule comprising a shell material encapsulating a center-filled core material, wherein the shell material is formed of a carbohydrate in a glassy state, and especially to methods and apparatus for making the seamless capsules for producing food products and topically applied products employing the same.
2. Description of the Prior Art
Traditionally, seamless capsules formed of a shell material encapsulating a core material have been made by using as the shell material film-forming materials such as gelatin and gums. These shell materials present two disadvantages. First, they are formed from an aqueous solution. Consequently, when the capsules are formed, large amounts of water must be removed, requiring great amounts of energy and long drying times. Second, these shell materials dissolve slowly when the capsules are being consumed, thereby leaving a distasteful plastic film-like residue in the mouth.
Seamless capsules are usually made by simultaneously extruding the shell material and the core material through concentrically aligned nozzles. The extruded shell material and the extruded core material exit the nozzles as a coaxial jet with the shell material surrounding the core material. The jet of the respective materials is fed into a downwardly flowing stream of cooled carrier liquid. While descending in the cooled carrier liquid, the coaxial jet breaks into droplets with the shell material encapsulating the core material. The droplets then solidify in the cooled carrier liquid to form seamless capsules. Such methods are disclosed, for example, in U.S. Pat. Nos. 4,251,195 and 4,695,466. However, when the shell material is a material that solidifies quickly, this prior art method is disadvantageous in that the shell material in the coaxial jet may solidify prior to encapsulation. As a result, seamless capsules may not be formed, and of the capsules that are formed some may not be spherical nor may they have a uniform size and shape.
An attempt to overcome this problem was proposed in U.S. Pat. No. 4,422,985, which describes a method that modifies the above-mentioned prior art method by introducing a coaxial triple jet, consisting of a heated circulating liquid surrounding the shell material which in turn surrounds the core material, into the cooled carrier liquid to allow encapsulation to take place. In this method, since capsule formation must still take place in the cooled carrier liquid, if any solidification of the shell material occurs prior to entering the cooled carrier liquid, encapsulation will not occur.
Other methods for making capsules typically involve using a screw extruder to extrude an emulsion containing the shell matrix and the material to be encapsulated. However, in such a process, it is difficult to make a capsule formed of a shell material encapsulating a center-filled core material. Instead, the encapsulated material is often in the form of globules that are distributed within the matrix. Other publications of interest in the formation of seamless capsules are mentioned below.
U.S. Pat. No. 2,857,281 describes a process for making a solid flavoring composition in the form of globular particles by extruding an emulsion containing a sugar base and flavor oil into droplets.
U.S. Pat. No. 3,971,852 describes a process for encapsulating oil in a cellular matrix that is formed of polyhydroxy and polysaccharide compounds. The oil is in an emulsified state with the cellular matrix, and the resulting emulsion is spray dried as droplets of the emulsion.
U.S. Pat. No. 5,009,900 discloses a process for encapsulating volatile and/or labile components with extruded glassy matrices, wherein the encapsulated material is distributed in the glassy matrices.
European Patent Application No. 0339958 discloses an antifoaming composition containing an outer shell of a meltable sugar in its crystalline state with an organopolysiloxane antifoaming composition imbedded therein. This composition is formed by melting a sugar base and dispersing the organopolysiloxane antifoaming composition in the sugar melt as the discontinuous phase. The melt is then solidified, thereby imbedding and entrapping the antifoaming composition, which is dispersed in the melt.
U.S. Pat. No. 5,300,305 relates to microcapsules that provide long lasting breath protection.
Of particular note is U.S. Pat. No. 5,595,757. The method described therein concerns the making of seamless capsules with a carbohydrate in a glassy state by providing a first duct located below a concentrically aligned multiple nozzle system. A coaxial jet is introduced into a flow of a heated carrier liquid within the first duct, thereby allowing the shell material to encapsulate the core material to form capsules in the heated carrier liquid. A second duct is located at least in part beneath the first duct, for receiving the flow of heated carrier liquid carrying the capsules from the first duct. A cooled carrier liquid is introduced into the second duct to form a flow of the cooled carrier liquid surrounding the capsules, thereby allowing the capsules to solidify.
In this prior art method, the cooled carrier fluid is purposely introduced concentrically with the heated carrier fluid to avoid turbulent flow which can damage the capsules. Because the fluids are therefore flowing in a laminar state, very little mixing of the heated carrier fluid and the cooled carrier fluid occurs. As a result of the laminar flow of the heated and cooled carrier fluids, capsule cooling will take place by conduction of heat from the hot stream to the cold stream.
However, while capsule cooling will take place, nonetheless heat conduction through laminar fluids is slow and therefore the length of the second duct carrying the cooled carrier fluid will need to be quite long, approaching 30 feet or more depending on the liquid flow rates. Excessively long ducts are needed in order to provide sufficient opportunity for the capsules to be properly cooled. In addition, it will not be possible to have a curvature in the duct (to reduce the space occupied by the capsule forming apparatus) until the capsules reach the solidification temperature since any contact with the walls of the duct prior to solidification will result in capsule deformation or blocking of the duct due to the insufficiently cooled capsules sticking along the wall.
It would therefore be a significant advance in the art of forming seamless capsules to provide a method of production which is cost efficient and does not require excessively long ducts to effect proper solidification of the capsules. Such a method would enable the production of a wide variety of products for consumption or application to the human body.